The invention concerns a polycondensate containing (I) at least a structural unit, which is an aromatic moiety bearing a polyether side chain comprising 9 to 41 alkylene glycol units, (II) at least a structural unit, which is an aromatic moiety bearing at least one phosphoric acid ester group and (III) at least a methylene unit (—CH.sub.2—), the polycondensate having a polycondensation degree of 10 to 75. Also concerned are building material mixtures containing said polycondensates and the use as dispersant for inorganic binders.